Arm 32bits arch docker support

[bugeaud]

Current version of Dockerfile seem to support arch x86_64 as x86_64 and aarch64 , armv8* and arm64 as aarch64.

    ARCHITECTURE="$(uname -m)" ; \
    case $ARCHITECTURE in \
    x86_64) ARCHITECTURE="x86_64" ;; \
    aarch64 | armv8* | arm64) ARCHITECTURE="aarch64" ;; \
    *) \
    echo "(!) Architecture $ARCHITECTURE unsupported" \
    exit 1 \
    ;; \
    esac ;\

Add a support for Arm 32 bits (like Arm7 for some raspberry pi and some NAS including ) variant look possible as it is also a supported arch of curl-impersonate

    ARCHITECTURE="$(uname -m)" ; \
    case $ARCHITECTURE in \
    x86_64) ARCHITECTURE="x86_64" ;; \
    aarch64 | armv8* | arm64) ARCHITECTURE="aarch64" ;; \
    arm | armv7*) ARCHITECTURE="arm" ;; \
    *) \
    echo "(!) Architecture $ARCHITECTURE unsupported" \
    exit 1 \
    ;; \
    esac ;\

See also #1466 for some prerequisite cleaning on the Dockerfile